I cleaned my EGR and trottle body last summer for 1buck. 1 can of carb cleaner safe for O2 sensors cost me a buck. I also, replaced the PCV at a cost of, I think, 12 bucks; which I purchased from St. Charles isuzu.
Old EGR use to be vaccum actuated. And when they went bad, then yes they needed to be replaced. The new solinoid ones usually only need to be cleaned.
As for fuel injection service, I run one bottle of Chervron Techron concentrate every 3k in my gas.
I'm also, planning on adding sea foam (per their instructions) to the oil once every 6 months about 250-500 miles before I change the oil.
Isuzu's really like to build up carbon. And when they do they idle ruff, and burn oil.
If you haven't changed the fuel filter yet, plan on doing it after you use the Techron.
-Ryan